It is common knowledge that 80% of the income of telecommunication comes from 20% of the clients, namely the big clients. Now, the importance of the big clients to the operators is self-evident in the increasing telecommunication competition. The enterprises and big clients require high-standard quality of telecommunication services due to their special service needs, and the focus of competition among operators for attracting the big clients is to provide value-added services capable of bringing significant benefits to the big clients while satisfying the basic requirement of voice service and data service, and the Central Exchange (Centrex) service is one of the popular value-added services.
The so called Centrex service regards some aggregative users as a user group and provides the group with various service functions, such as calling each other in the group with short numbers. Herein, the short number is the number valid only in the group and usually has fewer digits. At present, however, the Centrex service provided by a stored-program control switch is only allowed to be used within the exchange. That is to say, extensions can call each other with short numbers only when they are in the same user group of one exchange. Users belonging to one aggregative client but covered by Centrex of different exchanges have to call each other with the uniform numbers in the Public Switched Telephone Network (PSTN), which is a long number.
However, users belonging to one aggregative client but covered by different exchanges may desire to call each other with short numbers as well. Then Wide Area Centrex (WAC) needs to be provided for the aggregative client. WAC is to combine the Centrex of different switch nodes into a virtual cross-region private network through physical and signaling connection. Though such a private network is dispersed in regions, it is similar to a single Centrex in performance and use. That is to say, WAC users also have two numbers: a long number and a short number. Besides the basic calling and complementary services of the PSTN, the users in the group can enjoy many special complementary services similar to those provided by a Private Automatic Branch Exchange (PABX), such as calling each other via short numbers within the group. Further, a telephonist can be configured in each group to assist out-group, into-group and in-group calling. A call center can also be established to assist the calling of many Centrex groups simultaneously.
WAC service can be implemented through the Intelligent Network(IN) in the prior art, namely the so called 600 service, in which multiple cities are covered by the intelligent network such that users could call each other with short numbers. Such a service is in fact a result of combining WAC and the Virtual Private Networking (VPN) of the IN service.
The structure of a WAC system implemented through the IN is illustrated in FIG. 1, including users 10, 11 and 12, Local Switch (LS) 22, Service Switch Point (SSP) 30, and Service Control Point (SCP) 40, wherein LS can be classified into two types, one is LS21 which supports attribute judgement and number transformation for WAC users, and the other is LS22 which does not support attribute judgement and number transformation for WAC users. In addition, SCP 40 includes the long number and short number corresponding table, which is used for saving the corresponding relationship between the long numbers and the short numbers of the WAC users.
The process of using LS21 which supports attribute judgment and number transformation for WAC users in the prior art is hereinafter described in detail: Provided that user 10, who has the short number 5001 and long number 5550888, wants to call a cross-region user 12 who has the short number 7001 and long number 7770888 in the same group. At this time, user 10 may dial the short number 7001 to LS21 directly. After LS21 finds that the short number is not a short number of its own exchange, it adds 600N1N2 before the short number automatically, which changes the short number into 600N1N2+7001, then directs and connects the 600 route to SSP 30. After detecting the intelligent call, SSP 30 reports the intelligent call to SCP 40. SCP 40 finds the long number being called is 7770888 based on the long number 5550888 of the calling and the short number 7001 of the called. Then, SCP 40 instructs SSP 30 to connect to the long number being called 7770888. Thereafter, the connecting process between SSP30 and the called is the same as an ordinary call.
The process of using LS 22 which does not support attribute judgment and number transformation for WAC users in the prior art is as follows: Provided that user 11, who has the short number 6001 and long number 6660888, wants to call a cross-region user 12 who has the short number 7001 and long number 7770888 in the same group. At this time, user 11 needs to dial 600N1N2+7001 to LS 22, then LS 22 directs and connects the 600 route to SSP 30. Thereafter, the process is the same as above.
Besides being implemented by using the IN, WAC can be implemented by the method of distributed number memorization and transformation. In such a case, the inter-exchange relay signaling of the LS is the Integrated Services Digital Network (ISDN) User Part (ISUP) while the inter-exchange support for the extended Signaling Connection Control Part (SCCP) is required. As shown in FIG. 2, suppose that WAC is configured for two LS, every LS uses the switch of Internet Service Provider (ISP) board, and all the long number and short number corresponding tables of the WAC users in the group are saved in the switches used. The switches set up the communication path of SCCP via the PSTN. When an in-group call is made, the number of the group and the short number are sent to the ISP to inquire about the corresponding long number. The inquired long number may be the number of the same exchange or that of another exchange, and an in-exchange call or a cross-exchange call is implemented after an analysis of the long number. Herein, route data of the Message Transfer Part (MTP) ,which enable the telephone station to conduct cross-switch management of the data of the WAC users in the group and obtain phone bills across exchange by means of SCCP signaling ,are configured between the LS,.
In such a manner of implementation, the user data of each LS in the WAC need to be maintained and synchronized. The specific process of the data maintenance is as follows: When the user data in the WAC group are revised by a Background Administration Module (BAM) of a switch of an LS exchange and the WAC telephone station, the long number and short number corresponding table of the WAC group on the ISP board of the LS is revised. Meanwhile, the long number and short number corresponding tables relating to the WAC group on the ISP boards of other exchange are also revised through SCCP signaling so as to implement automatic cross-exchange user data maintenance. The specific process of the data synchronization is as follows: The long number and short number corresponding table of the WAC group on the ISP board will trigger the function of synchronized checking manually or periodically, which compares the long number and short number corresponding table with those saved in other exchanges within the WAC group to determine whether the tables are the same. If the tables are not the same, synchronized revision is performed, respectively, according to the data of the exchange to which the user belongs.
At present, WAC service can already be provided for users of PSTN, Public Lands Mobile Network (PLMN), and Next Generation Network (NGN) simultaneously.